<template>
  <el-upload
    class="avatar-uploader"
    action="https://jsonplaceholder.typicode.com/posts/"
    :show-file-list="false"
    :on-success="handleAvatarSuccess"
    :before-upload="beforeAvatarUpload"
  >
    <img v-if="imageUrl" :src="imageUrl" class="avatar" />
    <i v-else class="el-icon-plus avatar-uploader-icon"></i>
    <div class="mask_box">上传新头像</div>
  </el-upload>
</template>



<script>
export default {
  data() {
    return {
      imageUrl: ""
    };
  },
  methods: {
    handleAvatarSuccess(res, file) {
      this.imageUrl = URL.createObjectURL(file.raw);
    },
    beforeAvatarUpload(file) {
      const isJPG = file.type === "image/jpeg";
      const isLt2M = file.size / 1024 / 1024 < 2;

      if (!isJPG) {
        this.$message.error("上传头像图片只能是 JPG 格式!");
      }
      if (!isLt2M) {
        this.$message.error("上传头像图片大小不能超过 2MB!");
      }
      return isJPG && isLt2M;
    }
  }
};
</script>

<style>
.avatar-uploader .mask_box {
    width: 178px;
    height: 178px;
    line-height: 178px;
    position: absolute;
    top: 0px;
    left: 0px;
    background-color: rgba(0, 0, 0,0);
    opacity: 0;
    color: white;
    transition: all 0.4s;
}
.avatar-uploader:hover .mask_box{
    opacity: 1;
    background-color: rgba(0, 0, 0,0.76);
}
.avatar-uploader .el-upload {
  border: 1px dashed #d9d9d9;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.avatar-uploader-icon {
  font-size: 28px;
  color: #8c939d;
  width: 178px;
  height: 178px;
  line-height: 178px;
  text-align: center; 
}
.avatar {
  width: 178px;
  height: 178px;
  display: block;
}

</style>